New host shift from human to cows within Staphylococcus aureus involved in bovine mastitis and nasal carriage of animal's caretakers.

Staphylococcus aureus is a commensal and pathogen of both humans and bovines. While the epidemiology of both groups has been extensively studied individually, little is known about the potential zoonotic transfer from animal strains to human being and vice versa. To determine the S. aureus prevalence of bovine mastitis in Algeria and the zoonotic transfer of strains to human beings, mastitis milk samples were collected, and professionals in a close contact with bovines were nasal swabbed. S. aureus isolates were all characterized by methicillin resistance and spa-typing. DNA microarrays analysis was performed on a subset of strains in order to detect other virulence factors, including toxins, and to assign the isolates to theirs MLST clonal complexes. Overall, 116/222 (52.3%) cows suffered from mastitis, whose 38.8% (45/116) infected with S. aureus. Human nasal carriage was of 38% (49/129), with only 4 MRSA carriers (3.1%). A higher diversity of spa-types was observed in human (35/50) than in bovine (18/67) isolates, with a predominance of clonal complexes CC97 and CC22 in bovines. The typical animal clone CC97 was occasionally detected in human beings. Conversely, the CC22 S. aureus clone largely switched from humans to bovines. Our study highlights the potential dynamics of animal and human S. aureus strains in the farm environment in Algeria, which may represent a health threat in both populations.

High levels of Staphylococcus aureus and MRSA carriage in healthy population of Algiers revealed by additional enrichment and multisite screening.

The purpose of the research is to characterize Staphylococcus aureus colonization in healthy population of Algiers, to assess the impact on diagnostic performance of systematic additional broth enrichment, and to ascertain the additional benefits of multiple site screening. In order to more accurately determine the prevalence of S. aureus colonization, the swab specimens from multiple screening sites were incubated in brain-heart broth before agar plating. From 2009 to 2011, 1176 samples were collected from 459 participants (201 adults and 258 children). The additional enrichment detection step significantly increased S. aureus detection rates (p < 0.0001). S. aureus nasal detection was positive in 37.8% of adults, and the addition of throat samplings significantly increased the S. aureus detection rate up to 54.7% (p < 0.001). S. aureus nasal detection was positive in 37.6% of children. The addition of throat samplings in children significantly increased the S. aureus detection rate up to 53.1% (p < 0.001) and that of anal samplings up to 59.7%. The overall prevalence of methicillin-resistant S. aureus was 5.2% (3% of adults and 7% of children). spa typing of all isolates revealed a diverse but strongly clonal S. aureus population structure. This approach involving multiple anatomical sampling sites and an additional enrichment of the swabs before conventional culture significantly increases the detection rate of S. aureus carriers and may prove valuable to improve global S. aureus infection prevention.

Immunogenicity of toxins during Staphylococcus aureus infection.

BACKGROUND: Toxins are important Staphylococcus aureus virulence factors, but little is known about their immunogenicity during infection. Here, additional insight is generated. METHODS: Serum samples from 206 S. aureus-infected patients and 201 hospital-admitted control subjects were analyzed for immunoglobulin (Ig) G binding to 20 toxins, using flow-cytometry based technology. Antibody levels were associated with polymerase chain reaction-defined presence of toxin genes in homologous S. aureus isolates. RESULTS: IgG levels directed to exfoliative toxin (ET) A, ETB, gamma hemolysin B (HlgB), leukocidin (Luk) D, LukE, LukS, staphylococcal enterotoxin (SE) A, SEE, SEH, SEI, and SElM were higher in S. aureus-infected patients than in control subjects (P < .05). Furthermore, in the S. aureus-infected patient group, IgG levels were higher if genes encoding ETA, ETB, SEA, SEC, SEH, SElQ, toxic shock syndrome toxin-1 (TSST-1), or Panton-Valentine leukocidin (PVL) were present in the infectious isolate (P< .05). Levels of anti-SEA IgG increased during infections with sea-positive (median fluorescence intensity from 11,555 to 12,388; P<.05) but not sea-negative strains. In addition, anti-LukS IgG levels increased during skin and soft-tissue infections with luk-PV-positive (median fluorescence intensity from 15,231 to 15,911; P<.05) but not luk-PV-negative strains. Bacteremia was associated with sea (odds ratio, 3.4; 95% confidence interval, 1.2-10.0) and tst (odds ratio, 5.7; 95% confidence interval, 1.6-20.8). Skin and soft-tissue infections and bone and joint infections were associated with luk-PV (odds ratio, 2.5; 95% confidence interval, 1.2-5.2). CONCLUSIONS: Many toxins are expressed in vivo and recognized by the immune system during staphylococcal infections, suggesting their involvement in S. aureus pathogenesis.